It’s also the Maine Maritime Museum’s new exhibit on mechanized marine propulsion.

“Heavy Metal: The Revolution Evolution in Marine Propulsion” opened last Saturday at the 243 Washington St. museum and will run through Nov. 8.

“It’s actually a good opportunity for us to pull out a lot of our engines that have been tucked away,” Chris Hall, the museum's curator of exhibits, said last week. “A lot of people ask about our marine engines, and we have a fairly extensive collection, so it was a nice opportunity to feature that stuff.”

An extension of the exhibit, which includes diesel engines, has also been opened under the Percy & Small mill across the shipyard.

The engine evolution runs from steam-powered machines through more modern devices such as gasoline engines. Steam power was largely institutional, Hall said, requiring an engineer and trained people, a sophisticated organization to make everything work correctly.

“Gasoline came around," he said, "and all of a sudden everybody and their brother is getting their own engines, and this was very exciting."

The transition to a more affordable source of power around the turn of the 20th century opened the door for many Maine manufacturers to produce the new engines, and it also had pivotal cultural ramifications.

“Gasoline basically changed the whole balance of power in society, really,” Hall said. “It allowed a lot of common people to end up making their life easier.”

The new engines were beneficial not only in marine vessels, but also on land in mills, dairies and sawmills, he noted: “It just made a lot of labor activity easier.”

Gasoline engines also affected recreational activities: you could go further and faster in a motor-powered boat than you could by rowing. Steam engines had, conversely, been “a rich man’s toy” when it came to recreation, Hall said.

Steam did continue in larger ships, such as military fleets. An example of this in the center of the display is a mammoth steam turbine device from a 1930s Bath Iron Works-built destroyer.

One-lungers, outboards and Z-drives are among other marine engine types on display.

“(The engines) are a pretty critical part of our day-to-day life, whether on land or on sea,” Hall said, “and there’s a lot of interesting technology but a lot of interesting social effects, too, and hopefully (museum visitors) will come away with some sense of both.”

The museum is open daily from 9:30 a.m. to 5 p.m. Admission is free to members and children under 5; others are charged a general admission fee good for two days of visits.